1. Field of the Invention
The invention pertains to the field of semiconductor devices. More particularly, the invention pertains to a semiconductor laser with a low beam divergence.
2. Description of Related Art
High power semiconductor lasers play an important role in telecommunication systems, serving as pumps, fiber amplifiers and in other applications.
To obtain a low power density per facet and a low beam divergence for an edge-emitting laser, generally an extended waveguide is used. However, significant narrowing of the far field pattern is limited by multi-mode laser radiation.
Prior art in the field of edge-emitting lasers with a low beam divergence includes the concept of a leaky wave diode laser that, in principle, obtains low beam divergence. An example of this prior art is U.S. Pat. No. 4,328,469, issued May 4, 1982, entitled “HIGH OUTPUT POWER INJECTION LASERS”. This patent discloses a heterostructure injection laser with an active layer sandwiched between a pair of intermediate index layers. A layer with a very thin low refractive index and high bandgap may be located between an active layer and an intermediate layer. The thin layer may be applied in various combinations to produce fundamental mode guiding effects.
The major disadvantage of such devices is an extremely small confinement factor of the fundamental mode. One cannot fabricate a high power laser based on this effect. Therefore, there is a need in the art for a laser realizing both a low beam divergence and high power output.